1. Technical Field
Organic anti-reflective coatings and methods for forming photoresist patterns using the same are disclosed. The disclosed anti-reflective coatings improve uniformity of the photoresist pattern formed via ultra-fine pattern formation processes. More particularly, the disclosed organic anti-reflective coatings can prevent excessive generation of acid in an exposed portion of the pattern caused by the photo acid generator and can inhibit acid from diffusing up to the other unexposed portions which otherwise can lead to damage or collapse of the photoresist patterns. Methods for forming a photoresist pattern using the same are also disclosed.
2. Description of the Related Art
In recent years, as a resulted of advances in high integration and micro-fine formation of semiconductors, chemical-amplified photoresists have been created that make it possible to provide highly photo-sensitive and ultra-fine patterns, the photoresists a combination of a specified polymer having a specific structure sensitive to acid and an additional photo-acid generator.
Such chemical-amplified photoresists have a functional mechanism where the photo-acid generator generates acid at an exposed portion where the photoresist receives light from a light source and the generated acid then can react with the polymer during a further baking process after exposure which can lead to decomposition of the polymer at or near the exposed portion. In turn, the photoresist in the exposed portion includes the decomposed polymer which is then dissolved in the development solution then removed. With no generation of acid in the portion not exposed to light, the polymer is not decomposed and the photoresist is allowed to remain, thereby producing an accurate photoresist pattern.
However, the photoresist pattern formation process described above (hereinafter abbreviated as the “patterning method”) is problematic in that the acid generated in the exposed portion diffuses upward to another portion not exposed to light during the exposure process and/or a process for delaying after exposure (hereinafter referred to as “the time-delay process”). Thus, the acid can cause damage of the photoresist pattern existing in the unexposed portion (hereinafter referred to as “the non-exposure portion”). In particular, in a region, a so-called peri-region, having wider intervals between the photoresists in the non-exposure portion, the acid was excessively generated depending on the extent or area of the exposed portion. Accordingly, the acid can cause collapse of the photoresist pattern due to the deterioration of the polymer in the non-exposure portion.
Therefore, a strong demand exists for an improved technique to protect the non-exposure portion of photoresist from being damaged and/or collapse of the photoresist pattern due to acid-diffusion. In particular, conventionally known processes for preventing such an acid-diffusion phenomenon have used a chemical-amplified photoresist composition together with weak basic amine or amide compounds as an additive to neutralize the acid.
Because such amine or amide compounds have high light absorbance in an ultra-short wavelength region of less than 250 nm, for example, the wavelength of KrF (248 nm) or ArF (193 nm), the amine and amide compounds have the drawback of lowering the sensitivity of the photoresist compositions. Accordingly, there is still a need for a technical development for inhibiting collapse of photoresist pattern caused by acid-diffusion toward the non-exposure portion without reducing the sensitivity of the photoresist composition.
Meanwhile, in order to prevent damage to the photoresist pattern, which may occur by reflected light and diffracted light from the bottom film layer, an anti-reflective coating was introduced between the photoresist film and the bottom film layer. Typically, organic anti-reflective coatings are used, which are produced from a composition comprising a light absorbent agent, a cross-linking agent, a thermal acid generator and an organic solvent.
Briefly, these organic anti-reflective coating compositions form cross-linkage bonds between the cross-linking agent and the thermal acid generator. The resultant organic anti-reflective coating is not dissolved in a photoresist solvent, and can be favorably formed between the photoresist film and the bottom film layer. Since the organic anti-reflective coating includes the light absorbent agent having a higher light absorbance then the typical light source used in the photoresist pattern formation process, the anti-reflective coating can protect the photoresist pattern against reflected light and diffracted light from the bottom film layer, thereby improving uniformity of the pattern.
However, it was found that the introduction of such organic anti-reflective coatings described above only prevent damage to the photoresist pattern induced by the reflected light and the diffracted light from the bottom film layer. These coatings did not achieve inhibition of damage to the photoresist pattern caused by the acid-diffusion toward the non-exposure portion as described earlier.